Building upon our past research investigating the cognitive processes underlying the perception of individuals and groups, this proposal develops a conceptual framework for analyzing perceptions of groups in a variety of contexts and that has implications for stereotyping, self- stereotyping, and ingroup-outgroup differentiation, and outlines a series of investigations testing the viability of that conceptualization. The model gives central importance to the perception of entitativity- the perception that a number of individuals are, in some way, joined together in a social unit. Entitativity is conceived as varying considerably in groups, as well as in perceptions of groups, and those differences in perceived entitativity are postulated to underlie important differences in the way information about group targets in processed. The proposed research program (1) will investigate the information processing effects that derive from differences in perceived entitativity, (2) will distinguish among several types of groups and will investigate hypothesized differences between them in both the antecedents and the consequences of their perceived entitativity, (3) will investigate the role of perceived entitativity in stereotyping and ingroup-outgroup differentiations, (4) will extend our knowledge of entitativity through longitudinal studies examining the development of perceived entitativity over time, and (5) will provide clarification of the causal relations among important constructs through direct tests of the model. The results of the proposed research will considerably extend our knowledge of the processes underlying group perception and will integrate findings from disparate topic areas related to group perception.